Southern US storm, and a Tehuano wind event

December 15th, 2018 |

GOES-16 Low-level Water Vapor (7.3 µm) images, 13-15 December [click to play MP4 animation]

GOES-16 Low-level Water Vapor (7.3 µm) images, 13-15 December [click to play MP4 animation]

A large midlatitude cyclone moved from the southern High Plains to the Lower Mississippi Valley during the 13 December15 December 2018 period (surface analyses) — GOES-16 (GOES-East) Low-level Water Vapor (7.3 µm) images (above) showed the evolution of this system.

The corresponding GOES-16 Water Vapor images with plots of hourly surface wind gusts are shown below; peak wind gusts exceeding 50 knots occurred in parts of Colorado, New Mexico and Texas on 13 December.

GOES-16 Low-level Water Vapor (7.3 µm) images with hourly plots of surface wind gusts, 13-15 December [click to play MP4 animation]

GOES-16 Low-level Water Vapor (7.3 µm) images with hourly plots of surface wind gusts in knots, 13-15 December [click to play MP4 animation]

This event was unusually windy in South Texas and the Rio Grande Valley:


Another notable aspect of this storm was a very localized area of heavy snowfall just south of Sweetwater, Texas:


The remnant patch of snow cover was evident in VIIRS Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) imagery on 14 and 15 December (below). The heaviest snowfall occurred over an isolated ridge along the eastern edge of the Edwards Plateau, where elevations of 2500-2600 feet were about 500 feet higher than the adjacent rolling plains. Since snow is a very effective absorber of energy at the 1.61 µm wavelength, it appeared dark on the Snow/Ice imagery.

Topography, Suomi NPP VIIRS Visible (0.64 µm) and Near-Infrared "Snow/Ice" (1.61 µm) images on 14 December [click to enlarge]

Topography plus Suomi NPP VIIRS Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images on 14 December [click to enlarge]

Topography plus NOAA-20 VIIRS Visible (0.64 µm) and Near-Infrared "Snow/Ice" (1.61 µm) images on 15 December [click to enlarge]

Topography plus NOAA-20 VIIRS Visible (0.64 µm) and Near-Infrared “Snow/Ice” (1.61 µm) images on 15 December [click to enlarge]

The strong cold front associated with this storm moved rapidly southward across the western Gulf of Mexico on 14 December (surface analyses), crossing the terrain of the Isthmus of Tehuantepec in southern Mexico and emerging into the Gulf of Tehuantepec as a gap wind (known as a Tehuano wind). A curved rope cloud marking the leading edge of the Tehuano winds was evident on GOES-17 and GOES-16 “Red” Visible (0.64 µm) images (below).

* GOES-17 images shown here are preliminary and non-operational *

GOES-17 (left) and GOES-16 (right)

GOES-17 (left) and GOES-16 (right) “Red” Visible (0.64 µm) images [click to play animation | MP4]

A comparison of GOES-16 Visible imagery from 14 and 15 December (below) showed how far southwestward the gap winds spread out across the Pacific Ocean during those 2 days. Note that on 15 December there were ship reports with wind speeds of 50 knots, at 12 UTC and at 17 UTC.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images with surface and ship reports, 14-15 December [click to play animation | MP4]

NOAA-20 VIIRS True Color Red-Green-Blue (RGB) and Infrared Window (11.45 µm) images on 14 and 15 December as viewed using RealEarth (below) also showed the progression of the Tehuano wind rope cloud — the hazy signature of dust-laden air within the offshore flow was also apparent on the daytime True Color images.

NOAA-20 VIIRS True Color and Infrared Window (11.45 µm) images on 14 and 15 December [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images on 14 and 15 December [click to enlarge]

Metop-A and Metop-B ASCAT surface scatterometer winds across the western Gulf of Mexico [click to enlarge]

Metop-A and Metop-B ASCAT surface scatterometer winds across the western Gulf of Mexico [click to enlarge]

On 14 December, a sequence of EUMETSAT Metop-A and Metop-B ASCAT surface scatterometer winds (source) showed the cold front moving southward across the western Gulf of Mexico (above), and also showed the northerly gap wind flow just beginning to emerge into the Gulf of Tehuantepec around 1607 UTC (below).

Metop-A and Metop-B ASCAT surface scatterometer winds across the southern Gulf of Mexico and the Gulf of Tehuantepec [click to enlarge]

Metop-A and Metop-B ASCAT surface scatterometer winds across the far southern Gulf of Mexico and the Gulf of Tehuantepec [click to enlarge]

Severe thunderstorms in Argentina

December 10th, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm, top) and “Clean” Infrared Window (10.3 µm, bottom) images [click to play MP4 animation]

A comparison of GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) showed the development of thunderstorms well ahead of a cold front (surface analyses) that was moving northward across central Argentina on 10 December 2018. A Mesoscale Domain Sector had been positioned over that region in support of the RELAMPAGO-CACTI field experiment IOP15, providing imagery at 1-minute intervals. The northernmost storm (of a cluster of 3) featured a very pronounced overshooting top that was seen for several hours, briefly exhibiting infrared brightness temperatures as cold as -80ºC (violet enhancement) at 2133 UTC and 2134 UTC. Also noteworthy was the long-lived “warm trench” (arc of yellow enhancement) immediately downwind of the persistent cold overshooting top.

Plots of GOES-16 GLM Groups on the Visible and Infrared images (below) showed a good deal of lightning activity with this convection — especially in the leading anvil region east of the storm core. However, it is interesting to point out that there was a general lack of satellite-detected lightning directly over the large and persistent overshooting top. The GLM Groups were plotted with the default parallax correction removed, so the optical emissions of the lightning aligned with cloud-top features as seen on the ABI imagery.

GOES-16 "Red" Visible (0.64 µm, top) with GLM Groups and "Clean" Infrared Window (10.3 µm, bottom) images [click to play MP4 animation]

GOES-16 “Red” Visible (0.64 µm, top) with GLM Groups and “Clean” Infrared Window (10.3 µm, bottom) images [click to play MP4 animation]

A similar comparison of GOES-16 Visible and Near-Infrared “Snow/Ice” (1.61 µm) images (below) helped to highlight the formation of multiple Above-Anvil Cirrus Plume (AACP) features, which are signatures of thunderstorms that are producing (or could soon be producing) severe weather such as tornadoes, large hail or damaging winds. The appearance of gravity waves upshear (west) of the overshooting top was also very apparent.

GOES-16 "Red" Visible (0.64 µm, top) and Near-Infrared "Snow/Ice" (1.61 µm, bottom) images [click to play MP4 animation]

GOES-16 “Red” Visible (0.64 µm, top) and Near-Infrared “Snow/Ice” (1.61 µm, bottom) images [click to play MP4 animation]

Plot of severe weather reports [click to enlarge]

Plot of severe weather reports [click to enlarge]

There were several reports of hail with these particular thunderstorms (above), concentrated in the area between 35-36º S latitude and 62-65º W longitude. GOES-16 Visible images (below) showed this was the area under the path of the more northern storm with the prolonged overshooting top and the prominent AACP. This convection produced very large hail in Ingeniero Luiggi and General Villegas (located at 35.5º S, 64.5º W and 35º S, 63º W respectively) — see the tweets below for photos. On a side note, the large overshooting top began to take on an unusual darker gray appearance after 2230 UTC, possibly suggesting that boundary layer dust or particulate matter was being lofted to the cloud top by the very intense and long-lived updraft — the 18 UTC surface analysis showed that sites northwest of and south of the developing storms were reporting blowing dust.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images [click to play MP4 animation]

Additional GOES-16 animations of these storms can be found on the Satellite Liaison Blog.

A zoom-in of NOAA-20 VIIRS True Color Red-Green-Blue (RGB) imagery at 1835 UTC viewed using RealEarth  (below) showed the 3 discrete thunderstorms in the vicinity of Santa Rosa.

NOAA-20 VIIRS True Color RGB image at 1835 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB image at 1835 UTC [click to enlarge]

A toggle between NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1835 UTC (below) revealed the cold overshooting tops associated with each of the 3 thunderstorms. Also note the swath of wet soil in the wake of the southern storm, which appears darker in the True Color image and cooler (lighter shades of gray) in the Infrared image.

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1835 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1835 UTC [click to enlarge]

A toggle between NOAA-20 VIIRS Infrared Window (11.45 µm) images at 1835 UTC on 10 December and 0555 UTC on 11 December (below) showed the upscale growth into a large Mesoscale Convective System (MCS) that moved northeastward (eventually producing flooding in Rosario).

NOAA-20 VIIRS Infrared Window (11.45 µm) images at 1835 UTC on 10 December and 0555UTC on 11 December [click to enlarge]

NOAA-20 VIIRS Infrared Window (11.45 µm) images at 1835 UTC on 10 December and 0555 UTC on 11 December [click to enlarge]


===== 11 December Update =====

GOES-16

GOES-16 “Red” Visible (0.64 µm) images [click to play MP4 animation]

On the following day, GOES-16 Visible images (above) showed that additional severe thunderstorms developed across northern Argentina, in the general vicinity of a stationary front (surface analyses) east of Cordoba (SACO). Plots of GLM Groups (below) indicated that these storms produced a great deal of lightning.

GOES-16 "Red" Visible (0.64 µm) images, with GLM Groups plotted in red [click to play MP4 animation]

GOES-16 “Red” Visible (0.64 µm) images, with GLM Groups plotted in red [click to play MP4 animation]

The corresponding GOES-16 Infrared images, with and without plots of GLM Groups, are shown below. The coldest cloud-top infrared brightness temperatures were frequently colder than -80ºC, even reaching -90ºC (yellow pixels embedded within darker purple areas) from 1946, 1947 and 1948 UTC.

GOES-16 "Clean" Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 "Clean" Infrared Window (10.3 µm) images, with GLM Groups plotted cyan [click to play MP4 animation]

GOES-16 “Clean” Infrared Window (10.3 µm) images, with GLM Groups plotted cyan [click to play MP4 animation]

A NOAA-20 VIIRS True Color RGB image (below) showed the cluster of thunderstorms east of Cordoba at 1817 UTC.

NOAA-20 VIIRS True Color RGB image at 1817 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB image at 1817 UTC [click to enlarge]

A toggle between NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1817 UTC (below) showed the easternmost storm which produced a tornado at Santa Elena.

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1817 UTC [click to enlarge]

NOAA-20 VIIRS True Color RGB and Infrared Window (11.45 µm) images at 1817 UTC [click to enlarge]



Industrial and ship plumes in supercooled clouds

December 4th, 2018 |

MODIS and VIIRS

MODIS and VIIRS “Fog/stratus” BTD images [click to enlarge]

A sequence of nighttime MODIS and VIIRS “Fog/stratus” infrared Brightness Temperature Difference (BTD) images (above) revealed long plumes (darker shades of red) streaming southwestward for over 200 miles from their industrial point sources in the Mesabi Range of northeastern Minnesota on 03 December 2018.

During the subsequent daytime hours, a comparison of GOES-16 (GOES-East) “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm), Near-Infrared “Cloud Particle Size” (2.24 µm) and Shortwave Infrared (3.9 µm) images (below) showed signatures of these Mesabi Range plumes along with others emanating from industrial or power plant sources. A few ship tracks were also apparent across Lake Superior.

Particles emitted from the exhaust stacks at power plants and industrial sites (as well as ships) can act as efficient cloud condensation nuclei, which causes the formation of large numbers of supercooled water droplets having a smaller diameter than those found within the adjacent unperturbed supercooled clouds — and these smaller supercooled cloud droplets are better reflectors of incoming solar radiation, thereby appearing brighter in the Near-Infrared and warmer (darker gray) in the Shortwave Infrared images.

GOES-16

GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm), Near-Infrared “Cloud Particle Size” (2.24 µm) and Shortwave Infrared (3.9 µm) images [click to play animation | MP4]

On the following night, another sequence of MODIS and VIIRS “Fog/stratus” infrared Brightness Temperature Difference (BTD) images (below) highlighted a number of industrial and power plant plumes across Minnesota, northern Wisconsin and the Upper Peninsula of Michigan. The curved shape of many of these plumes resulted from boundary layer winds shifting from northerly to westerly as the night progressed.

MODIS and VIIRS "Fog/stratus" BTD images [click to enlarge]

MODIS and VIIRS “Fog/stratus” BTD images [click to enlarge]

During the following daytime hours on 04 December, a comparison of VIIRS Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images (below) showed 2 plume types across eastern Nebraska. There were several of the brighter/warmer plumes similar to those noted on the previous day across Minnesota/Wisconsin/Michigan — but one large plume originating from industrial sites just east of Norfolk (KOFK) had the effect of eroding the supercooled cloud deck via glaciation (initiated by the emission of particles that acted as efficient ice nuclei) and subsequent snowfall. This is similar to the process that creates aircraft “distrails” or “fall streak clouds” as documented here, here and here.

VIIRS Visible (0.64 µm), Near-Infrared

VIIRS Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images [click to enlarge]


Farther to the east over Ohio and Pennsylvania, another example of the 2 plume types was seen (below) — one plume originating from an industrial site near Cleveland was glaciating/eroding the supercooled cloud and producing snowfall, while another bright/warm supercooled droplet plume was moving southeastward from a point source located west of Indiana County Airport KIDI.

The Cleveland plume was captured by an overpass of the Landsat-8 satellite, with a False Color Red-Green-Blue (RGB) image viewed using RealEarth providing great detail with 30-meter resolution (below). A small “overshooting top” can even be seen above the industrial site southeast of Cleveland, with the swath of glaciated and eroding cloud extending downwind (to the southeast) from that point.

Landsat-8 False Color RGB image [click to enlarge]

Landsat-8 False Color RGB image [click to enlarge]

Coincidentally, Landsat-8 also captured another example of a glaciating cloud plume downwind of the Flint Hills Oil Refinery south of St. Paul, Minnesota on 03 December (below). The erosion/glaciation of supercooled cloud extended as far south as Albert Lea, Minnesota. Similar to the Cleveland example, a small “overshooting top” was seen directly over the plume point source.

Landsat-8 False Color RGB image [click to enlarge]

Landsat-8 False Color RGB image [click to enlarge]

===== 08 December Update =====

The effect of this industrial plume glaciating and eroding the supercooled water droplet clouds over northern Indiana was also seen in a comparison of Terra MODIS Visible (0.65 µm), Near-Infrared “Snow/Ice” (1.61 µm) and Infrared Window (11.0 µm) images (below).

Terra MODIS Visible (0.65 µm), Near-Infrared

Terra MODIS Visible (0.65 µm), Near-Infrared “Snow/Ice” (1.61 µm) and Infrared Window (11.0 µm) images [click to enlarge]

===== 09 December Update =====



During the following daytime hours, GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm), Near-Infrared “Cloud Particle Size” (2.24 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.3 µm) images (below) showed a number of plumes from industrial sites (many of which were likely refineries) streaming southeastward and eastward over the Gulf of Mexico on 09 December. Note the lack of a plume signature in the 10.3 µm imagery.
GOES-16 "Red" Visible (0.64 µm), Near-Infrared "Snow/Ice" (1.61 µm), Near-Infrared "Cloud Particle Size" (2.24 µm), Shortwave Infrared (3.9 µm) and "Clean" Infrared Window (10.3 µm) images [click to play MP4 animation]

GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Snow/Ice” (1.61 µm), Near-Infrared “Cloud Particle Size” (2.24 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.3 µm) images [click to play MP4 animation]

Tornado outbreak in Illinois

December 1st, 2018 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with SPC storm reports plotted in red [click to play animation | MP4]

The largest December tornado outbreak on record for the state of Illinois occurred on 01 December 2018 (NWS St. Louis | NWS Lincoln | NWS Quad Cities). 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the development of supercell convection which spawned the severe weather. in addition to the tornadoes, SPC Storm reports included hail as large as 1.75 inch in diameter and wind gusts of 75 mph.

GOES-16 “Clean” Infrared Window (10.3 µm) images (below) showed that cloud-top infrared brightness temperatures were as cold as -55ºC (darker shades of orange) with the more vigorous thunderstorm overshooting tops.

GOES-16

GOES-16 “Clean” Infrared Window (10.3 µm) images, with SPC storm reports plotted in red [click to play animation | MP4]

Plots of 18 UTC and 00 UTC rawinsonde data from Lincoln, Illinois (below) indicated that the coldest overshooting top brightness temperature of -55ºC seen in GOES-16 Infrared imagery was representative of a height just above the calculated air parcel Most Unstabe (MU) Equilibrium Level (EL).

Plot of 00 UTC Lincoln, Illinois rawinsonde data [click to enlarge]

Plots of 18 UTC and 00 UTC rawinsonde data from Lincoln, Illinois [click to enlarge]

A sequence of MODIS (from Terra and Aqua) and VIIRS (from Suomi NPP and NOAA-20) Visible and Infrared images (below) provided 2 higher-resolution views of the pre-storm environment, plus 3 views during/following convective initiation. Unfortunately, the thunderstorms in Illinois were located along the far eastern edge of the instrument scans in the final 2 images.

Terra/Aqua MODIS and Suomi NPP/NOAA-20 VIIRS Visible and Infrared images [click to enlarge]

Terra/Aqua MODIS and Suomi NPP/NOAA-20 VIIRS Visible and Infrared images [click to enlarge]

Even though the convection in western Illinois was near the limb of NOAA-20 (mis-labelled as Suomi NPP) VIIRS swath at 2007 UTC — degrading the spatial resolution and introducing some parallax error — the coldest detected Infrared brightness temperature (-52C) was still several degrees colder than that detected by GOES-16 (below). The two images are displayed in different projections, but the enhancements use the same color-vs-temperature breakpoints.

Comparison of GOES-16 ABI and NOAA-20 VIIRS Infrared Window images at 2007 UTC [click to enlarge]

Comparison of GOES-16 ABI and NOAA-20 VIIRS Infrared Window images at 2007 UTC [click to enlarge]